Cartridge Overall Length - a definitive explanation please

[ovenpaa]

The manufacturing process for mass produced comparator inserts is such that there are going to be differences and this is why I say to people do not compare your results to others when using a comparator, the results are yours only and for your benefit only.

I machine my own comparators and hold the bore ID to a very tight tolerance and will typically see repeatability better than 0.0005" on a good digital or analogue vernier however if I were to leave the comparator in the sun all day and compare it to one that came out of the fridge there may be slight differences in measurements due to material expansion, also the repeatability of the devise is very dependent on operation and a repeated pressure is required to give consistent results.

Another consideration is many comparators have no provision for aligning the case head to the bullet so you will see parallax errors creeping in.

[ColinR]

I machine my own comparators and hold the bore ID to a very tight tolerance and will typically see repeatability better than 0.0005" on a good digital or analogue vernier .....

Presumably that 0.0005" is also determined by the bullet dimensions at the ogive, which seems surprising.

[ovenpaa]

I should have been clearer, when testing the same loaded round typically the vernier gives a repeated zero for the reference round when repeatedly removed and placed back into the comparator. This is with no faffing around such as rotating the loaded round or trying to align the cartridge head correctly.

The ones I build take a reference from the Ogive based upon the point at which the bullet engraves the lands. I also build my own seater stems to pick up from a similar point, yes I do see variances across some makes of bullet however some are surprisingly accurate and I often see maximum seated variances of .0005"

Batching the bullets prior to seating also makes a difference.

[Alpha1]

I use one of ovenpaa,s comparators it's far superior to the hornady offering.

[ovenpaa]

We are just going through the pain, costs and potential minefield that is design registration for our comparator systems amongst other things, a very sad state of affairs necessitated by recent events here in the UK.

[Alpha1]

Don't take this the wrong way ovenpaa but what is the advantage of registering your design and going to all that expense what is stopping some one else turning out a exact copy and just calling it by another name. Or is this a patent thing.

[ovenpaa]

Alpha1, they can do that however the legal ownership of the design would be mine.

Patents are very different and effectively if I was to place as idea/description/drawing of something new in the Public Domain I would not be able to Patent it. This is the main reason for me no longer discussing anything new I am working on and why I have shelved a few ideas recently, I am not prepared to spend countless hours on design, development and testing just to see my work copied and placed on the market by other people here in the UK.

Apologies to the OP for the hijack.